I bought a second car for utility use; B6000, 1994, p/u, standard trans. Only when starting and running when the engine is cold, it runs very rough and difficult to idle. At normal operating temperatures the idle is somehwat okay and it seems to run fine. Also, the tach seems to jump up and down (even when the engine is at normal operating temps). Lastly, it appears the vehicle is running very rich as you can smell unburnt gas (moreso when engine is cold) and the tailpipe is packed with black residue. I suspected maybe an air type hose may have come loose or damaged thereby creating an uneven fuel mixture when the engine is cold. Couldn't find any hoses to speak of to support that theory. Can you assist?

I'll leave this open, check the air horn for cracks, that is the big plastic rubber thing that connects the air filter to the throttle. If it leaks air, it will run rough. Also, the plug wires will do it and the intake manifold sucking in air will do it, you can check that by pouring water on it or spraying wd40 on it, if it evens out when running, you have found a leak. Hope this helps. I'll leave this open, check the air horn for cracks, that is the big plastic rubber thing that connects the air filter to the throttle. If it leaks air, it will run rough. Also, the plug wires will do it and the intake manifold sucking in air will do it, you can check that by pouring water on it or spraying wd40 on it, if it evens out when running, you have found a leak. Hope this helps.

I will try your recommendations. By the way, can the fuel pump relay have anything to do with cold performance problems? I will try your recommendations. By the way, can the fuel pump relay have anything to do with cold performance problems?